Contents lists available at ScienceDirect Inorganica Chimica Acta journal homepage: www.elsevier.com/locate/ica Research paper Search for the shortest intermetallic Tl—Tl contacts: Synthesis and characterization of Thallium(I) coordination polymers with several mono- and bis-cyanoximes Scott Curtis a , Brett Lottes a , Daniel Robertson a , Sergey V. Lindeman b , Nikolay Gerasimchuk. a, ⁎ a Missouri State University, Department of Chemistry, Temple Hall 456, Springfield, MO 65897, United States b Department of Chemistry, Marquette University, Milwaukee, WI 53233, United States ARTICLE INFO Keywords: Thallium(I) coordination polymers Cyanoxime ligands X-ray analysis Thermal analysis Electronic spectra Raman spectra ABSTRACT Five new Tl(I) coordination compounds based on aryl monocyanoximes, such as phenylcyanoxime – HPhCO, 1, 2- fluorophenylcyanoxime – H(2F-PhCO, 2, 3-fluorophenylcyanoxime – H(3F-PhCO), 3, of TlL composition, and aryl biscyanoximes, such as 1,3-cyanoxime (benzene) – H 2 (1,3-BCO, 4 and 1,4-cyanoxime (benzene) – H 2 (1,4- BCO), 5 of Tl 2 L stoichiometry were synthesized and characterized using spectroscopic methods, thermal stability studies, and X-ray analysis. All obtained complexes represent coordination polymers of different complexity, ranging in dimensionality from 1D in Tl(2F-PhCO) to 3D in Tl 2 (1,3-BCO). The most interesting feature of all synthesized complexes is the formation of Tl 2 O 2 rhombs: non planar and non-centrosymmetric in Tl(PhCO), and planar and centrosymmetric in the other three compounds. These rhombi are interconnected, forming zigzag and ladder-type polymers in which very short thallophilic Tl—Tl distances were observed. Thus, in the structure of Tl 2 (1,3-BCO) the closest distance between metal centers was found to be 3.670 Å. This is the second shortest on- record intermetallic contact in non-organometallic and non-cluster, but Werner type complexes, and is close to that in metallic thallium: 3.456 Å. In all five new coordination polymers the central atom has a stereo-active 6 s 2 lone pair that significantly distorts the shape of the coordination polyhedron of Tl(I). The first time, Tl–O vibrations in Tl 2 O 2 rhombs were observed in Raman spectra of the obtained complexes. Thermal analysis studies evidenced stability of all complexes, but Tl(PhCO), to ∼200 °C. The Tl 2 (1,3-BCO) compound demonstrates properties of the high energy compound, and violently exothermically decomposes at ∼255 °C with the release of a significant amount of kinetic energy. The final product of anaerobic decomposition of all studied Tl-cyanoximates is me- tallic thallium sponge. 1. Introduction In recent years, there has been an upturn in research on a subset of macromolecules known as coordination polymers [1–4]. They can take on a variety of morphologies, being divided according to their di- mensionality into 1D, 2D and 3D polymers, with different properties and potential applications. Thus, one-dimensional columnar, zigzag chains, ladder-type, or stacks, are interesting from the standpoint of electrical conductivity [5–8], while two-dimensional sheets of co- ordination polymers are interesting for catalysis applications [9–11] and magnetic coupling/ordering [12,13]. A specific type of three-di- mensional coordination polymers, known as metal–organic frameworks (MOFs), contains large lattices that are mostly empty scaffolds with pores for potential application for gas sorption [14–31]. These struc- tures can accommodate the most important gas, H 2 , which is the key component of ‘hydrogen economy’ [32–34]. Coordination polymers have attracted a fair deal of attention for their optical and elastic properties, as well as their potential for use in molecular electronics [35], and in certain cases, have even been shown to have antimicrobial properties [36]. A number of coordination poly- mers that have been synthesized have been shown to exhibit electro- luminescence [37], which has garnered attention with regard to the use of the transition metals for coordination polymers with this property, owing to the energy of the triplet state that the metals exhibit [38–42]. Substantial attention with regard to coordination polymers has been given to the transition metals [43–52] with the main group elements largely disregarded recently. Of particular interest in the main group metals is a small cluster of 5p and 6p elements, specifically Tl, Pb, Sb, and Bi, that can exist in two accessible oxidation states which are two electrons apart. Thallium, however, has shown a unique ability among https://doi.org/10.1016/j.ica.2020.119597 Received 1 December 2019; Received in revised form 14 March 2020; Accepted 16 March 2020 ⁎ Corresponding author. E-mail address: NNGerasimchuk@MissouriState.edu (N. Gerasimchuk.). Inorganica Chimica Acta 508 (2020) 119597 Available online 28 March 2020 0020-1693/ © 2020 Elsevier B.V. All rights reserved. T